with β˜ (t) capturing the time-effect embedded in the systematic risk com- ponent of the jth security. Apparently, coefficients βj and β˜ (t) in (2) are
not identifiable unless we impose { β˜ (t)dt = 0. In this respect, the para-
metric beta-estimate can be regarded as the mean value of beta for the whole period under consideration. Thus, dependent on the time-period it is additively increased or decreased by the estimate of its non-parametric counterpart. In other words, the estimated beta-coefficient in period k is
given by βˆ
= βˆ + βˆ˜(k).